Highly efficient single-layer organic light-emitting devices based on a bipolar pyrazine/carbazole hybrid host material

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 2; no. 14; pp. 2488 - 2495
• Main Authors: Liu, Yuan, Cui, Lin-Song, Xu, Mei-Feng, Shi, Xiao-Bo, Zhou, Dong-Ying, Wang, Zhao-Kui, Jiang, Zuo-Quan, Liao, Liang-Sheng
• Format: Journal Article
• Language: English
• Published: 01.01.2014
• Subjects: Carbazoles; Charge; Devices; Excitation spectra; Maximum power; Organic light emitting diodes; Pyrazines; Trapping
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/C3TC32301C

Organic light-emitting diodes (OLEDs) have attracted tremendous interest and have already become a prevalent technology in MP3 players, smartphones and cameras. In response to the calls for the large-scale application of OLEDs, the complicated and costly processes for preparing a device is a major challenge which should be addressed. Herein, a novel bipolar host material, 26PyzCz , which contains a pyrazine/carbazole hybrid, has been designed and synthesized. 26PyzCz -based single-layer (SL) fluorescent (F)–phosphorescent (P) OLEDs with various colors have been successfully fabricated. Green and orange SL phosphorescent OLEDs (PHOLEDs) have exhibited efficiencies as high as 63.3 and 62.1 cd A −1 at 1000 cd m −2 , and 55.7 and 53.8 cd A −1 at 10 000 cd m −2 , respectively. Meanwhile, a SL warm white OLED based on fluorescent blue and phosphorescent orange has demonstrated excellent performance, with a maximum current efficiency of 27.5 cd A −1 and a maximum power efficiency of 21.6 lm W −1 . In addition, the charge carrier behavior have been evaluated by impedance spectroscopy, which revealed that the dopant trapping effect plays a critical role in charge balance and exciton generation in the SL PHOLEDs.